EP0492945A1 - Wabenförmiges Heizgerät mit Katalysator - Google Patents

Wabenförmiges Heizgerät mit Katalysator Download PDF

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Publication number
EP0492945A1
EP0492945A1 EP91311723A EP91311723A EP0492945A1 EP 0492945 A1 EP0492945 A1 EP 0492945A1 EP 91311723 A EP91311723 A EP 91311723A EP 91311723 A EP91311723 A EP 91311723A EP 0492945 A1 EP0492945 A1 EP 0492945A1
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EP
European Patent Office
Prior art keywords
honeycomb
honeycomb structure
oxide
honeycomb heater
catalyst
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EP91311723A
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English (en)
French (fr)
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EP0492945B1 (de
Inventor
Fumio Abe
Junichi Suzuki
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NGK Insulators Ltd
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NGK Insulators Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/9454—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/63—Platinum group metals with rare earths or actinides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • F01N3/2013—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using electric or magnetic heating means
    • F01N3/2026—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using electric or magnetic heating means directly electrifying the catalyst substrate, i.e. heating the electrically conductive catalyst substrate by joule effect
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present invention relates to a honeycomb heater and a catalytic converter wherein a honeycomb structure is coated with a specific catalyst composition.
  • Honeycomb heaters of the above-described type can be employed as heaters for domestic use, such as hot air heaters, or as industrial heaters, such as preheaters used for control of automobile exhaust emission.
  • the above-described catalytic converters can be applied for use in automobile exhaust emission control.
  • Catalytic converters for use in automobile exhaust gas control must have a predetermined temperature or above when operated so as to cause its catalyst to do catalytic action. Hence, the catalyst must be heated when the temperature thereof is not sufficiently high, i.e., at the beginning of running of a vehicle.
  • Such techniques for heating the catalyst have been proposed in, for example, Japanese Utility Model Laid-Open No. 6760 ⁇ 9/1988.
  • This disclosed technique is a catalytic converter comprised of a metal monolithic catalyst disposed upstream of and adjacent to a main ceramic monolithic catalyst.
  • the metal monolithic catalyst comprises an electrically conductive metal substrate with alumina coated thereon.
  • a honeycomb substrate having an unit (monolithic) structure is coated with a catalyst composition which comprises zirconia loaded with a platinum-group metal, a refractory inorganic oxide such as activated alumina, and a rare earth element oxide such as a cerium oxide.
  • a purification catalyst for exhaust gas which comprises a honeycomb substrate with a catalyst composition coated thereon is disclosed, the catalyst composition containing a refractory inorganic oxide in a form of particles such as alumina and zirconia whose average particle diameter ranges 0 ⁇ .5-20 ⁇ ⁇ m; and supporting 5-30 ⁇ % platinum by weight and 1-20 ⁇ % rhodium by weight
  • Japanese Utility Model Laid-Open No. 6760 ⁇ 9/1988 does not disclose any adequate catalyst composition specifically, though it is important that a metal monolithic catalyst which is electrically conductive and is disposed upstream of the main monolithic catalyst should have the light-off performance at low temperature, thermal resistance and durability against poisonous substances such as Pb and P.
  • Both the catalysts for purifying exhaust gas disclosed in Japanese Patent Laid-Open Nos. 156545/1988 and 185451/1988 were not developed for the heater use; therefore, when they are used for coating a heater, the endurance and the like of the heater on such a bad condition as at high temperature needs to be developed.
  • An object of the present invention is to provide a honeycomb heater and a catalytic converter which eliminate the aforementioned problems associated with the prior techniques.
  • the present invention provides a honeycomb heater comprising , a honeycomb structure having a large number of passages, at least two electrodes for energiging the honeycomb structure, provided on the honeycomb structure, a catalyst composition carried on the honeycomb structure, which contains zirconia powder loaded with at least Rh beforehand, an inorganic heat-resistant oxide and a rare earth element oxide.
  • the catalyst composition contains zirconia powder loaded with at least Rh beforehand and oxide powder comprising a mixture of a heat-resistant inorganic oxide and a rare earth element oxide loaded with at least one kind of platinum group element(s) beforehand.
  • the present invention further provides a catalytic converter wherein the above-mentioned honeycomb heater is disposed upstream or downstream of a main monolithic catalyst, or between the main monolithic catalysts.
  • a honeycomb heater having a resistance adjusting means such as a slit or slits between the electrodes is able to raise the temperature of exhaust gas quickly when the temperature of exhaust gas is still low, that is, the beginning of running of a vehicle; and therefore is preferred.
  • composition of the honeycomb structure in the present invention consists essentially of 2-30 ⁇ % Al by weight, 10 ⁇ -40 ⁇ % Cr by weight, and Fe accounting for most of the remainder.
  • a honeycomb structure employed in the present invention is produced by forming metal powders into a honeycomb configuration and then by sintering a formed honeycomb body.
  • Fig. 1 is a perspective view showing an embodiment of a honeycomb heater.
  • honeycomb heater disposed upstream or the like of the main monolithic catalyst have the following properties above all:
  • the catalyst on the honeycomb heater needs to have excellence in 1) light-off performance at low temperature; 2) the three-way catalytic performance at high temperature; 3) heat resistance; and 4) durability against poisonous substances.
  • Some method has to be come up with so as to solve the problem that the heat resistance of Rh- ⁇ Al2O3 (ordinarily used) in a catalyst declines owing to strong interaction between Rh and ⁇ Al2O3 especially in an oxidizing atmosphere. It is also important to prevent the decline of the durability against poisonous substances caused by adhesion of Pb and P in exhaust gas on the upstream side.
  • the substrate of the honeycomb heater needs to have excellence in 1) quick heating; 2) heat resistance; 3) oxidation resistance; 4) corrosion resistance during catalyst preparation; and 5) strength and thermal shock resistance (especially, having no telescope phenomenon).
  • a catalyst composition which contains zirconia powder loaded with at least Rh beforehand, a heat-resistant inorganic oxide and a rare earth element oxide.
  • the zirconia powder (Rh-ZrO2) loaded with Rh has the advantage of increasing the heat resistance because of the adequate interaction between Rh and ZrO2.
  • ZrO2 powder having a specific surface area of 5 m2/g - 10 ⁇ 0 ⁇ m2/g is suitable.
  • employing ZrO2 stabilized by addition of 1-8 mol of Y2O3 is preferable from the viewpoint of heat resistance.
  • the proportion of Rh to ZrO2 is preferably 0 ⁇ .0 ⁇ 1-15% by weight as far as the light-off performance, steady state performance, durability and so on are concerned. It is more preferably 0 ⁇ .0 ⁇ 1-1% by weight and most preferably 0 ⁇ .0 ⁇ 3-0 ⁇ .5% by weight in order to use the expensive Rh at the least necessary amount and to maintain the durability at a high level.
  • the preferable percentage of the zirconia powder with Rh contained in the catalyst composition is 5-50 ⁇ % by weight from the viewpoint of dispersion of Rh. Also, from the viewpoint of durability and the production cost, 10 ⁇ -30 ⁇ % by weight is preferable, since the ZrO2 material is expensive.
  • the heat-resistant inorganic oxide can be selected from alumina (Al2O3), silica (SiO2), titania (TiO2), zirconia (ZrO2) and their compound oxide.
  • the heat-resistant inorganic oxide preferably contains at least alumina. More preferably, it contains more than 70 ⁇ % alumina by weight.
  • Alumina can be used of any type among ⁇ , ⁇ , ⁇ , ⁇ , ⁇ , ⁇ , ⁇ .
  • alumina having a specific surface area of 10 ⁇ 0 ⁇ m2/g or more (mostly ⁇ type) is preferably employed.
  • a small amount of alumina having a specific surface area of 20 ⁇ m2/g or less (mostly ⁇ type) is blended with above-mentioned alumina.
  • Y or lanthanoide type elements are employedo CeO2, La2O3 and their compound oxide show a high purification efficiency for an exhaust gas generated even under various air-to-fuel ratios, because they are able to display their oxygen-storage ability.
  • the amount of the additional rare earth element oxide is preferably 2-35% by weight of the heat-resistant inorganic oxide such as alumina. Thus heat resistance of the heat-resistant inorganic oxide can be increased further.
  • the composition (the mixture) of a heat-resistant inorganic oxide and a rare earth element oxide is made to contain at least one kind of platinum group element selected from Pt, Pd, Rh, Ru, Ir and Os, by a known method.
  • the catalytic composition loaded with said platinum group element(s) beforehand is employed is most preferable because durability will be increased and because the step of impregnating with the platinum group element (noble metal) during preparing a catalyst can be omitted; and therefore, the metallic honeycomb heater can be prevented from corroding.
  • the noble metal with which the composition of a heat-resistant inorganic oxide and a rare earth element oxide is loaded preferably contains 0 ⁇ .1-10 ⁇ % Pt and/or Pd by weight, because they will not easily interact with Rh on ZrO2; and therefore, durability will be improved.
  • the total amount of the noble metal(s) loaded on the honeycomb heater with catalyst is preferably 0 ⁇ .5-1.6g per volume unit (l) of the honeycomb heater, and the total amount of Rh is preferably 0 ⁇ .0 ⁇ 2-0 ⁇ .3 g/l.
  • the weight ratio of Rh to other platinum group element(s) is preferably 1/19-1/5, from the viewpoint of the catalytic purification activity, durability and production cost.
  • the preferable ratio of the catalyst composition supported on the honeycomb heater is 35-230 ⁇ g/l.
  • the ZrO2 powder with Rh and the mixture of the heat-resistant inorganic oxide and the rare earth element oxide may take either a form of mixture, or a form of respective layers.
  • the mixture of the heat-resistant inorganic oxide and the rare earth element oxide includes the composite oxide thereof.
  • rhodium salt such as rhodium nitrate and rhodium chloride which contains required amount of Rh is loaded on ZrO2 powder, followed by calcining at 40 ⁇ 0 ⁇ -80 ⁇ 0 ⁇ °C. If the calcining temperature is under 40 ⁇ 0 ⁇ °C, the salt may not decompose sufficiently. If the temperature is over 80 ⁇ 0 ⁇ °C, undesirable Rh dispersion might occur.
  • the metallic honeycomb is liable to corrode during impregnation with the platinum group element(s).
  • alloying Rh is promoted while driving and durability is decreased, because the powder of Rh-ZrO2 is loaded by impregnation with other platinum group element(s) such as Pt and Rd.
  • a preferable method is that the heat-resistant inorganic oxide is loaded by impregnation with the platinum group element(s) beforehand, using an aqueous solution of the platinum group salt.
  • More preferable method for durability is that after mixing the heat-resistant inorganic oxide and the rare earth element oxide, for example, by wet method and subsequent calcining, the resultant composite oxide is impregnated with Pt and/or Pd.
  • the above-mentioned method is an example of coating the honeycomb heater in a mixture state with the ZrO2 powder containing Rh, the mixture powder of the heat-resistant inorganic oxide and the rare earth element oxide with platinum group element(s).
  • Each powder can be also coated on the honeycomb heater in a layered form having a desired film thickness.
  • honeycomb heater It is important to coat the honeycomb heater with the above-mentioned catalyst composition. To set up the range of both composition and structure of the honeycomb heater itself is also very important on practical use.
  • the substrate of the honeycomb heater As a honeycomb structure, the substrate of the honeycomb heater, a metallic sintered structure produced by forming a powder material into a honeycomb configuration and sintering the formed body is preferred.
  • the so-called powder metallurgy and extrusion are preferably employed, because of their simple process and low cost; moreover, since the structure has a unitary (monolithic) body, no telescope phenomenon occurs, and uniform heating can be achieved.
  • the honeycomb structure may have a heat-resistant metal oxide, such as Al2O3 or Cr2O3, coated on the surface of the cell walls and that of the pores thereof to enhance resistance to heat, oxidation and corrosion.
  • a heat-resistant metal oxide such as Al2O3 or Cr2O3, coated on the surface of the cell walls and that of the pores thereof to enhance resistance to heat, oxidation and corrosion.
  • any material, ceramic or metal, capable of generating heat when energized can be used as the material of the honeycomb structure employed in the present invention
  • the use of metal enhances the mechanical strength and is thus preferred.
  • metals include stainless steel and materials having a composition of Fe-Cr-AI, Fe-Cr, Fe-Al, Fe-Ni, W-Co, Ni-Cr or the like.
  • the composition being composed of 2-30 ⁇ % Al, 10 ⁇ -40 ⁇ % Cr and Fe accounting for most of the remainder by weight is preferred because of low cost and high resistance to heat, oxidation, corrosion and strength.
  • B, Si, Cu, on Sn can be added as a sintering promoter.
  • a rare earth element can be added up to 5% by weight to improve the resistance to oxidation.
  • the honeycomb structure employed in the present invention may be porous or non-porous.
  • a porous honeycomb structure is preferred because a catalyst layer can be closely adhered to such a honeycomb structure, and hardly peels off the honeycomb structure even when a difference in the thermal expansion between the honeycomb structure and the catalyst composition exists.
  • the metal honeycomb structure the basic body of the honeycomb heater, will be prepared in the manner described below.
  • Fe powder, Al powder and Cr powder, or alternatively powders of alloys of these metals are mixed to prepare a metal powder mixture having a desired composition.
  • the metal powder mixture is blended into an organic binder, such as methyl cellulose or polyvinylalcohol, and water to produce a readily formable mixture. That mixture is then formed into a shape of a desired honeycomb configuration by extrusion.
  • an antioxidant such as oleic acid
  • powders of metals which are subjected to anti-oxidation process may be employed.
  • the formed honeycomb body is fired in a non-oxidizing atmosphere at a temperature ranging between about 10 ⁇ 0 ⁇ 0 ⁇ and 140 ⁇ 0 ⁇ °C.
  • the organic binder is decomposed and thereby removed with the aid of Fe or the like which acts as a catalyst, and a good sintered body can therefore be obtained.
  • a heat-resistant metal oxide is then coated on the surface of the cell walls and that of the pores of the obtained sintered body by any of the following methods:
  • heat-treatment conducted at a temperature ranging between 90 ⁇ 0 ⁇ and 110 ⁇ 0 ⁇ °C is preferred.
  • the resistance adjusting means provided on the honeycomb structure may take on any of the following forms:
  • the honeycomb heater of the present invention is produced by providing electrodes on the outer periphery or inside of the metal honeycomb structure obtained in the manner described above by means of brazing or welding.
  • Electrodes' is used in this application to refer to any terminal through which a voltage is applied to the honeycomb heater.
  • the electrodes include the direct bonding of the outer peripheral portion of the heater to a can body and terminals for grounding.
  • the resistance thereof will preferably be held between 0 ⁇ .0 ⁇ 0 ⁇ 1 ⁇ and 0 ⁇ .5 ⁇ .
  • the honeycomb structure employed in the present invention may have any honeycomb configuration
  • the honeycomb structure employed in the present invention may be porous or non-porous.
  • the porosity of the metal honeycomb structure will preferably be held between 0 ⁇ and 50 ⁇ % by volume with most preferable porosity being less than 25% by volume.
  • honeycomb structure is employed in this application to refer to an integral body having a large number of passages partitioned by the walls.
  • the passages may have any cross-sectional form (cell shape), e.g., a circular, polygonal or corrugated form.
  • the honeycomb heater of the present invention is produced as mentioned above. If it is disposed upstream (in front) of the main monolithic catalyst, the honeycomb heater would be poisoned by Pb and P very much. Therefore, a protective film being porous of Al2O3, ZrO2 or the like is preferably put in the thickness of 5-20 ⁇ ⁇ m on the catalyst composition carried on the honeycomb heater in order to prevent direct interaction between the poisoning substances and the precious metal; consequently to improve durability.
  • the obtained honeycomb structure had a porosity of 22% by volume.
  • the electrodes 11 were provided on the outer wall 10 ⁇ of the thus-obtained honeycomb structure having an outer diameter of 90 ⁇ mm ⁇ and a length of 25 mm, as shown in Fig. 1 Also, six slits 12 having a length of 70 ⁇ mm were formed in the honeycomb structure in the axial direction of the passages (the slits provided at the two ends had a length of 50 ⁇ mm) at intervals of seven cells (about 10 ⁇ mm). Zirconia type heat-resistant inorganic adhesive was filled in an outer peripheral portion 13 of each slit 12 to form an insulating portion.
  • honeycomb heater substrate II having a composition of Fe-25Al(% by weight). This substrate II had a porosity of 30 ⁇ % by volume.
  • honeycomb heater substrate III having a composition of Fe-20 ⁇ Cr (% by weight). This base III had a porosity of 3% by volume.
  • alumina powder containing ceria was impregnated aqueous solutions of dinitrodiamine platinum, palladium nitrate and rhodium nitrate, in the containing amount of Pt, Pd and Rh shown in Table 1. Then the resultant powder was dried at 120 ⁇ °C for 16 hours; calcined at 650 ⁇ °C for 1 hour; thus ceria alumina powder containing platinum group element(s).
  • the obtained ZrO2 powder containing Rh and ceria alumina powder containing platinum group elements were wet-milled (acetic acid was added as a deflocculant) in the weight ratios shown in Table 1 to obtain a slurry for loading.
  • the honeycomb heater base I was loaded with the slurry by coating plural times and then fired at 525°C for 3 hours to obtain catalysts No. 1-11.
  • the loading amount was made to be 140 ⁇ g/l.
  • Rh-containing ZrO2 powder which had obtained in the same manner as in Procedure A, was added commercially available desired ⁇ -Al2O3 powder having a BET specific surface area of 20 ⁇ 0 ⁇ m2/g, a mixture of cerium acetate and ceria powder and acetic acid as a deflocculant.
  • the resulting mixture was milled in a pot mill to obtain a slurry for loading.
  • the honeycomb heater base was loaded with this slurry by coating plural times and fired at 525°C for 3 hours after drying; an aqueous solution of dinitrodiamine platinum was impregnated into the catalyst layer covering the honeycomb heater base; the resultant catalyst layer loaded with platinum was fired at 525°C for 3 hours to obtain catalyst No. 12.
  • the catalyst No. 2 which had been obtained in Procedure A was coated with the ZrO2 powder, which had been used in Procedure A, as a protective film in the thickness of 10 ⁇ ⁇ m to obtain a catalyst No. 13.
  • ⁇ -Al2O3 powder having a BET specific surface area of 20 ⁇ 0 ⁇ m2/g was added a mixture of cerium acetate and ceria powder in an amount of 10 ⁇ parts by weight in terms of ceria. There were further added 150 ⁇ parts by weight of water and a little amount of acetic acid. The resulting mixture was milled in a pot mill to obtain a slurry, with which a honeycomb heater base was coated plural times, and fired at 525°C for 3 hours.
  • the resultant sintering article was loaded with dinitrodiamine platinum, palladium nitrate and rhodium nitrate by impregnation in the containing amount of Pt, Pd and Rh shown in Table 1. Then catalysts Nos. 16 - 18 were obtained by firing at 525°C for 3 hours after drying.
  • a catalyst No. 19 was obtained in the same manner as in Procedure A, except that ZrO2 powder containing Rh was used.
  • Catalytic converters were produced by disposing the catalysts no. 2 and 17 (preheaters with a catalyst) which had been obtained in the present invention on the upstream (front) side of commercially available three-way catalysts -namely, main monolithic catalysts (honeycomb structures which had a volume of 1.31; whose carrier was ceramic; which consisted of square cells having a rib thickness of 6 mil and a cell density of 40 ⁇ 0 ⁇ cells/in2). These catalytic converters were subjected to aging on the same conditions as in Durability test a .
  • the exhaust gas in the case of A/F 14.6 had a composition (by volume) of 1.7% (CO), 2,760 ⁇ ppm (HC) (in terms of C), 950 ⁇ ppm (NO x ), 1.3% (O2), 0 ⁇ .6% (H2), 13.2% (CO2), 10 ⁇ .0 ⁇ % (H2O), 23 ppm (SO2) and the remainder (N2).
  • the catalytic converters which had been obtained Durability test b were used to evaluate the catalytic performance for exhaust gas at the beginning of operation of the engine.
  • every sample of the present examples was excellent in light-off performance and three-way characteristic, even after a durability test.
  • the catalytic performance of NO x was high because of interaction between Rh and ZrO2.
  • the catalysts No.1 and 4 which contained less Rh showed excellent performance as much as or more than the catalyst No. 18 which contained more Rh. Therefore, drastic cut of expenses can be made by reducing precious metal.
  • the catalyst No. 14 had a sufficient catalytic performance after a durability test, though, several cracks occurred in the cells owing to vibration and thermal shock during the durability test; the durability of the catalyst No. 15 was not sufficiently high. Consequently, it is preferable that a honeycomb heater base adequately composed be used. In the catalyst layer of the catalyst No. 15, separating of Fe and Cr was observed.
  • the honeycomb heaters and catalytic coverters of the present invention have excellence in the purification property for exhaust gas such as light-off performance at low temperature and three-way catalytic performance, heat resistance and durability against poisonous substances.
  • honeycomb heater of the present invention which has a specific composition is employed, there can be obtained a honeycomb heater and catalytic converter which have the rapid-heating ability, excellent resistance against heat, shock and so on.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Toxicology (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)
EP91311723A 1990-12-21 1991-12-18 Wabenförmiges Heizgerät mit Katalysator Expired - Lifetime EP0492945B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2413096A JP2848970B2 (ja) 1990-12-21 1990-12-21 ハニカムヒーター及び触媒コンバーター
JP413096/90 1990-12-21

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EP0492945A1 true EP0492945A1 (de) 1992-07-01
EP0492945B1 EP0492945B1 (de) 1995-09-06

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US (1) US5318757A (de)
EP (1) EP0492945B1 (de)
JP (1) JP2848970B2 (de)
AU (2) AU651158B2 (de)
CA (1) CA2057564C (de)
DE (1) DE69112799T2 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5500198A (en) * 1993-10-26 1996-03-19 Massachusetts Institute Of Technology Composite catalyst for carbon monoxide and hydrocarbon oxidation
WO2002022255A1 (en) * 2000-09-18 2002-03-21 Valtion Teknillinen Tutkimuskeskus Catalyst and method for the catalytic reduction of nitrogen oxides

Families Citing this family (40)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3506747B2 (ja) * 1992-12-15 2004-03-15 日本碍子株式会社 ハニカムヒーター
JP3281087B2 (ja) * 1993-02-10 2002-05-13 日本碍子株式会社 排ガス浄化用触媒
JP3210508B2 (ja) * 1993-12-14 2001-09-17 日本碍子株式会社 ハニカムヒーター
US5547641A (en) * 1995-01-10 1996-08-20 Caterpillar Inc. Catalytic converter exhaust section for an internal combustion engine
JPH08273805A (ja) * 1995-03-30 1996-10-18 Ngk Insulators Ltd 通電発熱可能なハニカム体
JP3345222B2 (ja) * 1995-07-21 2002-11-18 日本碍子株式会社 通電発熱用ハニカム体およびハニカムユニット
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US5318757A (en) 1994-06-07
EP0492945B1 (de) 1995-09-06
CA2057564A1 (en) 1992-06-22
AU651158B2 (en) 1994-07-14
DE69112799D1 (de) 1995-10-12
CA2057564C (en) 1999-04-06
JP2848970B2 (ja) 1999-01-20
AU7297794A (en) 1994-11-24
AU8980291A (en) 1992-06-25
DE69112799T2 (de) 1996-03-21
JPH04224220A (ja) 1992-08-13

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